1. Field of the Invention
The present invention concerns a method as well as an apparatus allowing an interventional procedure involving heart valves to be conducted using a robot-based x-ray device.
2. Description of the Prior Art
The reduction of the pumping power of one or both heart chambers is generally designated as a cardiac insufficiency. Cardiac insufficiency is not an actual illness, but rather is the result of various disease/pathology symptoms. As a result of cardiac insufficiency, the body and its organs do not receive the necessary amount of blood per unit of time. The vital organs are only insufficiently supplied with oxygen and nutrients.
Among the most important causes of cardiac insufficiency are illness of the coronary vessels (often after extended infarctions), hypertension that is insufficiently medically regulated, heart muscle illness, heart muscle infection (myocarditis), illness of the pericardium, and illness of the heart valves.
Congenital stenoses of one or more heart valves, or stenoses caused by other sources, such as, for example, calcium deposits, are frequent pathological conditions of the heart valves. Various types of interventional surgical procedures are known for addressing one or more of the above causes of cardiac insufficiency.
In the case of a pulmonary valve stenosis, the leaflets of the pulmonary valve are thickened, so that the opening of the valve is hindered. The right chamber therefore works against an increased resistance, and forms more muscle mass, i.e. it becomes hypertrophic.
In aortic valve stenosis, a narrowing or constriction of the discharge path of the left chamber occurs. The cause is a thickening of the valvular cusp and/or an underdevelopment of the aortic root. The constriction may be below the valve (sub-valvular), at the valve (valvular) or above the valve (supra-valvular). The left chamber works against an increased resistance and becomes thicker (becomes hypertrophic). Sub-valvular and supra-valvular aortic stenoses can generally be treated using balloon catheters.
Mitral stenosis is normally an acquired valve defect, and is almost always the result of rheumatic endocarditis.
Until the 1990's, heart valve stenoses normally were therapeutically treated by open heart procedures. Such procedures have high risks associated therewith as well as long recovery (convalescence) times for the patient.
The heart valves can be damaged by other illnesses, for example inflammation, influenza or cardiac infarction, to the extent that the valve must be replaced or surgically modeled.
Until recently, a replacement of a heart valve required an open heart procedure. Mechanical or biological heart valve prostheses were implanted (aortic valve, pulmonary valve) or the existing valve opening was surgically shaped (mitral valve and tricuspid valve). Such procedures also were associated with high risks and long recovery times (up to six weeks) for the patient.
More recently, methods have been developed to treat heart valve stenoses in a minimally-invasive manner by the use of specially designed catheters. In principle, all four heart valves are accessible for a balloon dilation (valvuloplasty), but dilation of the tricuspid valve is only rarely implemented, due to the relative rarity of tricuspid stenosis.
The basic steps of a number of known balloon dilation procedures are described below.
For balloon dilation in the case of pulmonary valve stenosis, after probing of the right or left pulmonary artery from the groin with an open-ended catheter, a relatively rigid guide wire is introduced. A special dilation catheter (valvuloplasty catheter) can be advanced via this guide wire after the catheter has been retracted.
This procedure is implemented under anesthesia, since filling of the balloon leads to a temporary interruption of circulation. In the case of less thickened valves, an excellent result with less residual resistance, and no or minimal insufficiency of the pulmonary valve, is achieved. In the case of a valve atresia, the targeted perforation of the valves by means of HF energy and subsequent balloon dilation is frequently possible.
Balloon dilation in the case of aortic valve stenosis resembles the procedure for balloon dilation in the case of pulmonary valve stenosis, in that a balloon catheter is advanced via a guide wire to the location of the valve. Generally, the probing is implemented in a retrograde manner, since the left ventricle is accessible via the stenotic aortic valve.
For balloon dilation in the case of mitral stenosis, the balloon catheter can be inserted into the mitral valve either in an antegrade manner from the left atrium (after transseptal puncture) or in a retrograde manner from the left ventricle. More recently, the antegrade procedure has prevailed. The size (area) of the opening (aperture) of the mitral valve can be doubled, for example, by means of balloon dilation.
A catheter suitable for this purpose is described in U.S. Pat. No. 4,819,751. Such catheters have the advantage of allowing a minimally-invasive cardiac procedure to be conducted therewith.
For approximately two years, methods in clinical testing allow a replacement or modeling of heart valves in a minimally-invasive manner by the use of special catheters.
Integration of an artificial heart valve into a stent that is placed in the aortic valve and the pulmonary valve with a catheter is described, for example, in the website www.corevalve.com. A detailed description can also be found in the article “Percutaneous Valve Therapies: Where We Are and Where We Are Going,” by Feldman (www.tct.com).
A suitable heart valve for this purpose is described in United States Patent Application Publication No. 2006/0074485.
The shape of the mitral valve and/or the valve opening thereof can be modeled with catheter-based tools, for example with the commercially available Carillon Mitral Contour System, available from www.cardiacdimension.com. This catheter is conducted through the coronary sinus, and the procedure is known as percutaneous mitral annuloplasty.
A detailed description of known methods for repairing mitral valves can be found in the article “Percutaneous Valve Repair: Update on Mitral Regurgitation and Endovascular Approaches to the Mitral Valve,” by Dieter.
A catheter device for insertion in an annuloplasty ring is described in PCT Application WO 2004/103233.
In contrast to the above-described diseases, diseases of the tricuspid valve are rare, but when found to exist, can be treated in procedures similar to those described above concerning the mitral valve.
A significant disadvantage of all of the recently developed minimally-invasive procedures is that they must be implemented using x-ray fluoroscopy, which shows only a 2D image of the heart and the catheter and tools located therein or proximate thereto. It is very difficult for a surgeon or cardiologist to mentally form spatial associations from such 2D images.
A further disadvantage associated with such known procedures is that when the catheter is clearly visible in such an x-ray image, the opening of the heart valve in question is only poorly visible, or vice versa. The opening can be shown more clearly by the injection of a contrast agent, but a significant number of patients are at risk of having an allergic reaction to conventional contrast agents.
Due to these limitations in the content of the displayed images, a risk exists that the stenosis will not be correctly opened, or an artificial (replacement) heart valve may not be correctly placed.
It is also known to conduct some of these procedures, or portions thereof, supported by extracorporeal or intracorporeal (ICE, TEE) ultrasound imaging, but generally this does not provide a sufficient image quality.
In theory, imaging in the context of the aforementioned known procedures could be improved by the use of a C-arm x-ray device, such as the CardDynaCT available from Siemens Medical Solutions. With this device, 2D soft tissue exposures as well as 3D high contrast exposures (with the injection of contrast agent) of a beating heart can be produced.
In practice, however, the aforementioned commercially available C-arm x-ray device, as well as other commercially available C-arm x-ray devices, does not provide adequate access to the patient in order to permit percutaneous heart valve procedures to be implemented by operating personnel.